[tjts1]

Originally Posted by Nerys

I do know on E10 my HC is just shy of max for failure of an emissions test. If I can find someone who will do it for me I would like to run that test with E0 and E10 and compare. I could have E0 in the car for this years inspection in a month but comparing that with YEAR old E10 data is not a very valid comparison.

Your O2 sensor is probably toast which would would also explain the poor running on E10. I've said it before and I'll say it again. Get your car fixed.

My smog check numbers before (top) and after (bottom) replacing my O2 sensor. Both tests were done on E10 in a 1992 mercedes with mechanical fuel injection (Kjet designed in the early 70s) and a closed loop O2 sensor. Hardly cutting edge stuff.

Originally Posted by Coyote X

The ethanol needs a different air fuel ratio to properly work. Even a the amount you get from running E10 changes the desired ratio from 14.7:1 to something like 14.1:1 I am just guessing on the numbers but that seems close to me.

The O2 sensor doesn't measure air fuel ratios. A simple narrow band which every car on the road has, measures the O2 content in the exhaust and compares it to open air (20.9%). EFI always strives to maintain stoich where all the O2 in the exhaust is consumed. From the Bosch EFI manual:
87 octane (AKI)= 14.8 afr
93 octane (AKI)= 14.7 afr
E10 = 14.2 afr
E85 = 9.87 afr
Propane (LPG) = 15.67 afr
The same O2 sensor will give a perfectly accurate switching point at stoich with any fuel, whatever the afr.

Originally Posted by Coyote X

The OBD1 computers only had a limited range they could deviate from the fuel table so they seem to be adjusting to the limit and that is where E10 is more or less happy with. It is close enough that there will be no extra room if there is the slightest problem with the car.

This is incorrect. Even the most basic EFI system from the 80s has at least 10% and usually much more room to adjust air density or fuel content based. Running on E10 (~3% extra fuel at lambda 1) is well within the limits of any EFI system.

Originally Posted by Coyote X

But a OBD1 system is really not much different than a carb system when it comes down to it other than the 10% or whatever feedback adjustment it can make on the fly from the O2 sensor depending on the car's computer setup.

This is gross generalization and blatantly wrong. OBD1 or 2 only deals with the diagnostic equipment. There were plenty of very advanced EFI systems during the OBD1 era. The original Civic SI stood for sequential injection in the late 80s. Bosch Motronic came on the scene around 1990 and went through several generations by 1996. Even LH 2.4 could handle sequential fuel fuel injection, coil on plug ignition, and VVT all from the same box in 1992. I would like to see a carburetor do that.

I don't know where you're getting your information.